1. Field of the Invention
The present invention relates to a fixing mechanism for optical glass. More particularly, the invention relates to an optical glass fixing mechanism useful for fixing a lens in a lens tube.
2. Description of the Prior Art
Hitherto, various methods have been employed to fix an optical lens in a lens tube for use in an electrophotographic copying apparatus and other image forming apparatus. Among them it has been well known and widely used to fit a lens clamp ring in a lens tube by means of threads. On the other hand, at present, there is an increasing tendency to make lens tubes employing plastic molding techniques. The most important merit they aim at obtaining by it is, of course, a reduction in cost. However, in practice, no satisfactory cost reduction is attainable thereby so long as there is used the conventional lens fixing method mentioned above. The cost involved in dies and many steps required for assembly diminish the merit derivable from the use of a molding technique. In particular, as for female screw, a die for under-cutting is required which makes the structure of dies larger and complicate. The above problem of dies is also applied to another arrangement of lens assembly comprisng a lens tube having a simple inner circumferential slot and a lens clamp ring member fitted in the slot. As for the assembling steps, the number of steps necessary for assembly is increased when the above thread engagement method is employed to fix the lens in the lens tube. This is because the clamp ring has to be rotated several turns to firmly fasten the lens in the lens tube.